WATER CONTENT AND INFRARED TRANSMISSION OF SIMPLE GLASSES*

Abstract

A bstract Since glasses, which are high in silica or boric oxide content, have high absorption in the region of 2.7 to 3.0 microns, a study of the transmission characteristics of several simple glasses has been made. Measurements of a variety of commercially available samples (5 mm. thick) of fused silica showed absorption in the 2.70‐micron band to vary from strong to essentially absent. Measurements of a number of samples (1 mm.) of fused boric oxide showed the 2.85 band to be variable and to be absent in some samples. The samples which did not show a minimum were prepared by bubbling the melt with boron trichloride to remove water and by casting between two pieces of platinum foil. The foil was removed in an anhydrous atmosphere at the time of measurement. Similar measurements on fused sodium tetraborate samples (1 mm.) showed the minimum at 2.95 microns to be variable but not completely removed. Bubbling was carried out with dry air in this case since boron trichloride reacts with sodium tetraborate. The above bands are attributed to the OH vibrational absorption introduced by the water content of the glass. It is suggested that the exact position of the band might be an indication of the strength of bonding with the principal components of the glass.